The changes on pedestrian-heavy lines 12, 17 and 44, including the elimination of a stop near Portland State University to allow drivers more distance before a challenging left turn, take effect Monday.

TriMet's announcement came a day after officials made an about-face on reviewing left-turn policies following an April crash that killed two pedestrians and injured three others in a downtown crosswalk.

More operation, training and route changes are expected as part of a sweeping safety review ordered by outgoing General Manager Fred Hansen.

"We're looking at immediate ways we can improve safety around stops and turns in downtown," said TriMet spokeswoman Bekki Witt. "This is an opportunity for us to question all of our old assumptions."

The Oregonian this week reported TriMet hasn't changed its operating procedures despite a history of left-turn crosswalk crashes, including one that cost a 68-year-old Portland woman her leg in January 2008. Transit agencies in other metropolitan areas have changed theirs after similar accidents.

A 2008 federal study also showed that bus-pedestrian collisions are more than twice as likely to happen during left turns for various reasons.

TriMet says it will look at requiring bus drivers to honk before turning and may ban many left turns to reduce collisions with pedestrians -- ideas that the agency had earlier insisted were not feasible.

The route changes planned for Monday will make some left turns much safer but won't eliminate them, Witt said.

As they began their safety review, TriMet officials said these routes, with their heavy pedestrian traffic, cried out for swift alterations.

On lines 12 and 44, TriMet will remove one left turn on Southwest Fourth Avenue but replace it with another.

Instead of turning left onto Harrison Street almost immediately after making the last stop on Fourth, 40-foot northbound buses will travel two blocks further and turn left onto Southwest Mill Street.

Currently, drivers of 12 and 44 buses have only a matter of feet to pull out of the stop on the right side of Fourth, cross two one-way lanes and turn left onto Harrison.

"It's a little tight," Witt said. "This will allow more room to get into position."

With westbound Line 17 buses, TriMet will eliminate the stop at Southwest Fourth Avenue and Hall Street because it comes just before a similar left turn. Witt said she didn't know how soon the agency might eliminate some left turns entirely, a proposition that seems especially daunting with downtown's one-way grids.

Details are expected soon on the police investigation and whether prosecutors will seek charges in the April 24 crash involving a left-turning No. 9 bus.

Danielle Sale, 22, of Vancouver and Jeneé Hammel, 26, of Gresham were crushed under the bus's wheels at Northwest Broadway and Glisan Street. A third person was hospitalized and two suffered minor injuries.

In response to a series of left-turn crashes, other cities have moved quickly to change operations. The Cleveland Regional Transit Authority, for instance, not only eliminated many left turns and required buses to honk before turns but also lowered side mirrors on some buses to improve driver visibility.

On Friday, Amalgamated Transit Union President 757 President Jonathan Hunt said the operators union was ready to support the changes as long as they don't create problems for drivers trying to stay on already-tight schedules.

"But obviously," Hunt said, "if we're having problems with left-hand turns, and there's a safer way to do it, we're absolutely going to support that."